The biggest WTF/LOL moment I've had so far was after I did the quest where you have to steal a horse from the Black-Briar lodge east of Riften. The quest went pretty well, and I got the horse to Letrush and successfully completed the quest. Then, just as I was leaving and Letrush was about to get on the horse, we get randomly attacked by an "afflicted refugee". This was in the middle of the night, in the woods with trees and brush blocking the view half the time, and I could hardly see what was going on, and all sorts of wild crap happened in the ensuing melee. I think I hit both Letrush and the horse with my sword, probably repeatedly on both counts since Letrush at least would have hit back and I probably continued hitting him thinking he was the attacking refugee. At some point I realized that the refugee was dead and I was fighting Letrush, who had sunk halfway into the ground; he was only visible from the waist up. I sheathed my sword when it seemed like I couldn't kill him, and he stopped fighting me, but he kept following me around and getting right in my face; he wouldn't go away, and would follow me when I tried to go away. He looked so ridiculous, down there sticking out of the ground looking up at me. So I attacked him again, trying to kill him and make him go away. I also attacked the horse and tried to kill it, just out of desperation. It was at this point that things became really weird/funny. The HORSE attacked Letrush. So, there's Letrush, the human stump half-stuck in the ground, fighting the horse that I delivered to him. Letrush loses the fight, and yells, at the horse, "I yield, I cannot best you!". The last I saw of them, Letrush was "running" away screaming and the horse was chasing him and trying to finish him off. I was just sitting there like "W... T... F... just happened here?", and then I finally set out to leave the Rift because I had incurred a 1,025 gold bounty in all this madness and I couldn't possibly pay it off right then.
On the one hand I was annoyed at how buggy things got, but on the other hand it was really quite funny, especially later when I wasn't feeling annoyed anymore. And the next time I went to Riften, after I had filled my pockets elsewhere, I managed to pay a guard something around 500 gold to get them to drop the bounty since I'm in the Thieves' Guild.
There was also a smaller WTF/LOL moment I had, where I was coming down from High Hrothgar and, somewhere along the road down the mountain, there was a very bizarre thing going on with a goat. It must have fallen from a higher area or something, because its front half was stuck in the ground like Letrush's lower half had been; only the goat's hindquarters and back legs were sticking out of the ground, and it was moving all over the place in an almost dancing motion with this sound effect continuously going on like it was running or otherwise hitting the ground. I attempted to kill it to make it stop, but nothing I did would work. So I just left. It wasn't still there the next time I came to the mountain.